An optochemical analyte sensor such as an oxygen sensor is based upon the principle of analyte-induced fluorescence or luminescence quenching of an organic dye, which is normally introduced into a polymer matrix. In particular, the polymer/dye mixture tailored for a given analyte is applied as a solid film to a substrate such as a glass plate or an optical waveguide.
A device was disclosed in WO 2005/100 957 A1 for determining and/or monitoring an analyte contained in a fluid process medium. The known device has a sensor with a measuring membrane, which possesses a porous support structure. A luminescent substance is embedded in the support structure and comes into contact with the process medium. Furthermore, a transmitting unit and a receiving unit are provided, wherein the transmitting unit transmits measuring radiation, and the luminescent substance is excited to emit luminescent radiation, and wherein the receiving unit detects the correspondingly generated luminescent radiation. A control/evaluation unit detects a concentration or partial pressure/pressure of the analyte in the process medium based upon the quenching of the luminescent radiation of the luminous substance. Luminescence is, incidentally, the generic term for the generation of optical radiation in a substance that occurs with the transition from an excited state to the basic state.
An oxygen sensor which is offered and marketed by the applicant is shown in FIG. 1 of the following description of figures. Given the gap-free seal between the sensor housing and sensor membrane, this sensor satisfies the demanding hygienic requirements placed upon sensors when they are used in, for example, the food industry. If the known oxygen sensor is, however, in a pipeline through which a medium containing an analyte flows, bubble formation can occur on the surface of the membrane facing the medium. Of course, due to the formation of bubbles on the surface of the membrane, the measured values for oxygen, as the analyte to be determined in the flowing medium, are significantly distorted.
A sensor cap was disclosed in DE 10 2011 088 012 A1 that has a convex shape facing the medium. The sensing element is fastened to a convex-shaped surface facing the medium. Neither the advantage of this convex shape nor the satisfaction of hygienic requirements is addressed in this patent application.